US3023278A - Four wire line concentrator circuit - Google Patents

Four wire line concentrator circuit Download PDF

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Publication number
US3023278A
US3023278A US44303A US4430360A US3023278A US 3023278 A US3023278 A US 3023278A US 44303 A US44303 A US 44303A US 4430360 A US4430360 A US 4430360A US 3023278 A US3023278 A US 3023278A
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US
United States
Prior art keywords
wire
gate
line
transmission
station
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US44303A
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English (en)
Inventor
Dennis B James
Kenneth P Kretsch
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
AT&T Corp
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Bell Telephone Laboratories Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to NL133409D priority Critical patent/NL133409C/xx
Priority to NL266047D priority patent/NL266047A/xx
Application filed by Bell Telephone Laboratories Inc filed Critical Bell Telephone Laboratories Inc
Priority to US44303A priority patent/US3023278A/en
Priority to BE600136A priority patent/BE600136A/fr
Priority to FR865239A priority patent/FR1292578A/fr
Priority to DEW30306A priority patent/DE1200377B/de
Priority to ES0268976A priority patent/ES268976A1/es
Priority to GB25219/61A priority patent/GB968107A/en
Priority to CH844361A priority patent/CH394309A/de
Application granted granted Critical
Publication of US3023278A publication Critical patent/US3023278A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/04—Selecting arrangements for multiplex systems for time-division multiplexing

Definitions

  • Telephone communication systems exclusive of toll transmission facilities generally employ two wire cornniunication paths.
  • a telephone subscriber station howu ever, is inherently a Ifour wire device in that it has a transmitter and receiver.
  • a subset. circuit located at the subscriber station converts the four wire transmitter and receiver circuit to a two wire circuit for transmission to the central office.
  • the adverse trans mission effects of two wire to fou-r wire conversion ⁇ are not of substantial importance; however, where communication is to be established between stations separated by great distances, amplification must be inserted in the transmission paths to overcome the inherent transmission losses ⁇ and in such systems two wire to four wire conversion presents certain problems.
  • ln space division toll transmission systems vi.e., systems which employ a plurality of transmission paths which are assigned to one call at a time
  • a repeating coil hybrid circuit is employed to make the conversion from two wire to four wire transmission.
  • Fou-r wire subscriber stations which employ independent send and receive paths avoid the two wire to four' wire conversion in the above-noted time division system; however, there are two ⁇ very serious problems attendant the use of four wire subscriber stations. These problems are concerned with the provision of side tone to a talking subscriber and the provision of communication between a mainstation and'y an extension of the main station.
  • theseZ energy between the transmitting leg and the receiving leg' to provide side tone to a talking subscriber can be achieved through the use of a unidirectional amplifier individual to and located at the subscriber station. Such.
  • side 'tone transmission tothe receiver of a four wire sub-v scriber station is accomplished by meansv of common* gating and storage means in a remote concentrator.
  • coupling between the transmitting leg of a four wire subscriber station and thereceiving leg thereof by way of common means comprising input gating means, storage means, and out-put gating means provides communication between a main ⁇ station 'and extension stations of a four wire telephone subscribers station;
  • the common receiving and sending means in a time division multiplex concentrator are separate means andthek coupling of energy from the yreceiving meansf'tothel sending means is minimized.
  • FIG. 2 is a schematic representation of a two wire subscriber station and the time division hybrid arrangements of the above-mentioned James et al. Patent 2,936,- 338;
  • FIG. 3 is a time diagram showing the time of operation of various elements of FIG. 2 and the effects of electrical termination of the hybrid of FIG. 2;
  • FIG; 4 is a time diagram of the sequence of events in the arrangements of FIG. 1.
  • time division hybrid circuit of FIG. 2 provides circuits having adequate transmission characteristics, including a sufficiently high return loss, for use in local telephone switching systems, there is, however, sufficient cross-coupling between the receive and send legs of the four wire transmission path to bring about a problem where stations separated by great distances are to be interconnected.
  • the subscribers station 250 has a subset circuit which is not shown, for converting the four wire transmitter and receiver circuit to a two wire circuit for transmission to the line circuit and the time division hybrid in the remote concentrator.
  • the line circuit includes the transmission bridge and scanning resistors 253,'the coil 254, the low pass filter 251 and the bidirectional transmission gate 252.
  • the common transmission bus 213, which is a portion of the time division hybrid, is employed alternately for transmitting from and to the subscribers station 250.
  • Other subscriber stations and line circuits are connected to the common transmission bus 213 as indicated in FIG. 2.
  • the means in the concentrator controller 290 for controlling the gates of FIG. 2 are not shown in detail; however, the times of operation of the various gates of FIG. 2 are shown in FIG. 3.
  • the time division system employs an order of time wherein a frame of 125 microseconds duration comprises 24 time slots and each time slot comprises 8 information bit times.
  • the line gate 252 is enabled lfor 41/2 bit times which is slightly more than one-half of the eight bit time slot.
  • the send gate 210 is enabled simultaneously with the enablement of the line gate 252; however, the send gate is released 11/2 bit times after it is enabled as this provides sufficient time to sample the information present at the subscribers line circuit and to store the sample on the capacitor 217.
  • the receive gate 224 and the line gate 252 are simultaneously disabled and immediately thereafter the capacitor 217 which was connected to the encoder during the time the receive gate 224 was enabled is now clamped to ground potential in preparation for receipt of the speech sample from the line served in the next succeeding time slot.
  • lines 1--4 are drawn to a first time scale while lines 5 8 are'drawn to a greater time scale.
  • line 5 of FIG. 3 it is seen that 125 microseconds pass between successive enablements of the receive gate 224-, when serving line 250, and from lines 2 and 3 of FIG. 3 it is seen that the line gate 252 and the send gate 210 are enabled just prior to each enablement of the receive gate 224. Accordingly, a line vis sampled for sending v slightly less than 125 microseconds after a speech sample is received from the distant station.
  • line 6 the lter is assumed to 'be perfectly terminated and it is seen that for various values of positive and negati-ve samples transmitted from the receive gate 224 through the line gate 252, the voltages at the filter due to the various values of speech sample will run down or reduce to zero by the time the line is sampled to send information to the distant station.
  • a perfect termination of ⁇ the lter is an ideal situation and line 7 of FIG. 3 shows the voltage at the line filter 251 for various values of received signal when the lter is unterminated or terminated in an extremely high impedance.
  • FIG. 3 shows the voltage at the line filter 251 for various values of signal when the
  • the ter mination of the line filter 251 resulting from a subscriber station and the connecting line is not ideal; however, it does not reach either of the two extreme cases set forth in lines 2 and 3 of FIG. 4 but rather is an approximation of the ideal case.
  • the received speech sample with reasonable lengths of line between the concentrator and the two wire subscriber station, runs down approximately 25 db below its original level; therefore, a signal in the order of 25 db below the received speech sample is added to or subtracted from the speech sample originating at the local subscriber and is encoded along with the subscribers speech sample.
  • the subscriber station equipment 250 does not electrically match the iilter 251 for all frequencies within the transmitted band; therefore, there are slight refl ections of the received signal from the subscriber sta tion back to the filter and these reflected signals are also encoded and retransmitted to the distant station.
  • FIG. l there is shown a four wire subscriber station and the common send, receive and side tone circuits in accordance with this invention. The details of the concentrator controller 137 for enabling and disabling the transmission gates at the appropriate times are not shown.
  • a subscribers main station 16@ comprising a transmitter 133 and a receiver 134; a subscribers extension 101 of the main station also comprising atransmitter 135 and a receiver 136; a transmitting line 132 from the subscribers sta tion to the concentrator; a receive line 131 from the concentrator to the subscribers station; a four wire line circuit comprising the transformer ⁇ 103, transmission bridge and scanningresistors 104 and 105, capacitor 106, the subscribers transmitting line gate 107, the subscribers receiving line gate 128, the receiving iilter 129, and receiving transformer 13G.
  • the capacitor 106 in shunt with coil 103 advantageously provides sufficient filtering for the four wire transmitting leg.
  • the concentrator common send cir-- 'cuit comprises the common bus 168, the transmitting 112, the clamp gate 113, and the sending line 114 which is connected to the encoder through an output send gate which is not shown.
  • the common receiving circuit comprises the amplifier 127 which is arranged to raise the output signal from the decoder to a desired output level, the series resistor 125, the coillZS, receive gate 124, the coil 123, and the receiving common bus 122.
  • a common side tone circuit comprising the side tone input gate 111, the side tone storage capacitor 118, the side tone clamp gate 119, transmission coil 117, and the side tone output gate 121 is employed to provide the desired coupling between the transmitting leg of a four wire subscribers station and the receiving leg thereof.
  • the means within the concentrator controller 137 for controlling the varioustransmission gates of FIG. 1 are not shown in detail and it is assumed that these gates are operated in accordance with the teachings of the above-noted James et al. application Serial No. 760,502, which is now Patent No. 2,957,949. The sequence of operation of the various gates is shown in FIG. 4.
  • a subscribers line is sampled to obtain information for transmission to the distant station via the encoder and to obtain a pulse amplitude modulation sample for transmission to the receiving leg of the four wire circuit via the common side tone circuit. Subsequently, the received sample from the decoder and the above-noted side tone sample are transmitted to the receiving leg of the four wire circuit.
  • the line send gate 107, the common send gate 11@ and the side tone in gate 111 are enabled and disabled simultaneously. Each of these gates is enabled for 11/2 bit times.
  • the common receive output gate 124, the side tone output gate 121, and the line receive gate 128 are all enabled one-half bit time after the send sampling has been completed and are disabled 21/2 bit times thereafter.
  • the clamp gates 115 and 116 are enabled for 2 bit periods starting one-half bitrperiod after the receive gates have been disabled.
  • the transmitting and receiving sequence is accordingly completed in 7 bit periods of the 8 bit repetitive office cycle. That is, the send gates are enabled for 11/2 bit times, the receive gates are subsequently enabled for 21/2 bit times and the clamp gates are enabled for 2 bit times.
  • the send and receive and the receive and clamp intervals in each case are separated by one-half bit times.
  • he energy sampled from the subscribers line capacitor 106 is simultaneously stored on the send capacitor 112 and the side tone capacitor 118. lf these capacitors are of equal electrical size, equal charges will be stored- 6 tant end may be arranged to provide any required amplitication.
  • the send gate and 4the side tone gate 111 arel simultaneouslyenabled and disabled and the sample* period of' 1% bits, i.e;, approximately .975 microsecondY is suicient to obtain a speech sample fromv a subscribers line circuit.
  • the receive period follows the send sample period time byapproxirnately .3 of armicrosecond and during the receive period, the energy on send capacitor 112 is transferred to the encoder, which is not shown', for conversion to a PCMv code for transmission tothe distant subscriber station and the sample from the side tone capacitor 118 is gated to the'receiving line lter 129 through gates 121 and 128 along with an information sample, if present, from the distant subscribers station.
  • the information is transmitted from the send leg of the four Wire subscribers station to the receive leg via the side tone input and output gates 111 and 112 and the side tone storage capacitor 118 on a pulse amplitude ⁇ modulation basis.
  • Communication from the concentrator to the central oice and from the central ofiice to the concentrator indicated herein to be on a pulse code modulation basis may also be on a pulse amplitude modulation basis.
  • the transmission advantages which accrue through the use of four wire subscriber stations in a time division multiplex telephone switching system are maintained without loss of the necessary side tone transmission and without loss of communication between a main station and an extension station.
  • the deiiciencies of a normal four wire subscriber station are overcome by means of the common side tone circuit including an input gate, a storage capacitor, and an output gate.
  • a time division telephone switching system having remote concentrators, the combination comprising a plurality of four wire subscriber stations having separate transmitting and receiving transmission means, a sending transmission means common to said plurality of stations; a receiving transmission means common to said plurality of stations; a side tone transmission means common to saidplurality of stations; means for selectively and simultaneously connecting said common sending means and said side tone means to said sending transmission means of one of said plurality of subscriber stations, and means for subsequently, selectively and simultaneously connecting said side tone means and said common receiving means to said receiving transmission means of said one of said plurality of said subscriber stations.
  • said side tone means comprises a first gate means connected to said common sending means, a
  • second gate connected to said common receiving means, means for storing an information sample, and means for conditioning said storage means.
  • a telephone switching system in accordance with claim 2 wherein said means for conditioning said storage means comprises gating means and resistive means connecting said storage means to a discrete potential source.
  • a time division telephone switching system having remote concentrators, the combination comprising a plurality of four wire subscriber stations having separate transmitting and receiving transmission means, a sending transmission means common to said plurality-of stations; a receiving transmission means common to said plurality of stations; a sidetone transmission meansvcommon to said plurality of stations; means for selectively transferring energy from said transmitting means ofsaid subscriber stations to said side tone transmissionA means, and means for selectively transferring energy from said side tone means to. said receiving transmission means of said four wire subscriber stations.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Sub-Exchange Stations And Push- Button Telephones (AREA)
  • Telephonic Communication Services (AREA)
  • Use Of Switch Circuits For Exchanges And Methods Of Control Of Multiplex Exchanges (AREA)
US44303A 1960-07-21 1960-07-21 Four wire line concentrator circuit Expired - Lifetime US3023278A (en)

Priority Applications (9)

Application Number Priority Date Filing Date Title
NL133409D NL133409C (xx) 1960-07-21
NL266047D NL266047A (xx) 1960-07-21
US44303A US3023278A (en) 1960-07-21 1960-07-21 Four wire line concentrator circuit
BE600136A BE600136A (fr) 1960-07-21 1961-02-13 Circuit concentrateur de lignes à quatre fils.
FR865239A FR1292578A (fr) 1960-07-21 1961-06-16 Circuit de centre de commutation à quatre fils
DEW30306A DE1200377B (de) 1960-07-21 1961-07-06 Schaltungsanordnung zum Herstellen eines Rueckhoerweges in Zeitmultiplex-Fernsprechvermittlungsanlagen
ES0268976A ES268976A1 (es) 1960-07-21 1961-07-11 Sistema de conmutaciën telefënica con divisiën de tiempo y con concentradores distantes
GB25219/61A GB968107A (en) 1960-07-21 1961-07-12 Improvements in or relating to time division telephone switching systems
CH844361A CH394309A (de) 1960-07-21 1961-07-18 Zeitmultiplex-Telephonsystem mit Konzentratoren, mit je einer Vielzahl Vierdraht- Teilnehmerstationen mit getrennten Sende- und Empfangseinrichtungen

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US44303A US3023278A (en) 1960-07-21 1960-07-21 Four wire line concentrator circuit

Publications (1)

Publication Number Publication Date
US3023278A true US3023278A (en) 1962-02-27

Family

ID=21931618

Family Applications (1)

Application Number Title Priority Date Filing Date
US44303A Expired - Lifetime US3023278A (en) 1960-07-21 1960-07-21 Four wire line concentrator circuit

Country Status (7)

Country Link
US (1) US3023278A (xx)
BE (1) BE600136A (xx)
CH (1) CH394309A (xx)
DE (1) DE1200377B (xx)
ES (1) ES268976A1 (xx)
GB (1) GB968107A (xx)
NL (2) NL266047A (xx)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3492435A (en) * 1965-08-07 1970-01-27 Bell Telephone Labor Inc Four-wire concentrator without separate control path
US3517133A (en) * 1965-07-26 1970-06-23 Int Standard Electric Corp Four wire telephone system using phantom signaling circuit

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE708943C (de) * 1934-03-14 1941-08-01 Lorenz Akt Ges C Verfahren zur UEbertragung von Nachrichten mit Verlagerung der Sprechstroeme auf Teilstrecken der UEbertragungsleitung in verschiedene Frequenzbereiche
DE738028C (de) * 1939-06-08 1943-07-31 Lorenz C Ag AEquivalente Teilnehmervierdrahtschaltung
DE754971C (de) * 1939-09-30 1953-05-18 Wilhelm Dr-Ing Ohnesorge Nachrichtenuebertragungssystem
GB841555A (en) * 1955-04-14 1960-07-20 Post Office Improvements in or relating to transmission systems
NL243662A (xx) * 1955-08-23
BE570722A (xx) * 1959-03-13
DE1113009B (de) * 1960-02-12 1961-08-24 Phil Habil Oskar Vierling Dr Einrichtung zum Mitsprechen und Mithoeren an Vierdraht- und Zweidrahtstromkreisen

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
None *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3517133A (en) * 1965-07-26 1970-06-23 Int Standard Electric Corp Four wire telephone system using phantom signaling circuit
US3492435A (en) * 1965-08-07 1970-01-27 Bell Telephone Labor Inc Four-wire concentrator without separate control path

Also Published As

Publication number Publication date
CH394309A (de) 1965-06-30
NL266047A (xx)
BE600136A (fr) 1961-05-29
NL133409C (xx)
ES268976A1 (es) 1961-12-16
DE1200377B (de) 1965-09-09
GB968107A (en) 1964-08-26

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